Childhood and adolescent nutrition outcomes among girls exposed to gender-based violence: A rapid evidence assessment of quantitative research

Background An emerging evidence base has explored the nutritional consequences of gender-based violence (GBV) perpetrated against girls during childhood/adolescence. We conducted a rapid evidence assessment of quantitative studies describing associations between GBV and girls’ nutrition. Methods We adapted systematic review methods and included empirical, peer-reviewed studies, published after 2000 (until November, 2022), that were written in Spanish or English and reported quantitative associations between girls’ exposure to GBV and nutrition outcomes. A variety of GBV forms were considered: childhood sexual abuse (CSA), child marriage, preferential feeding of boys, sexual IPV and dating violence. Nutrition outcomes included anemia, underweight, overweight, stunting, micronutrient deficiencies, meal frequency, and dietary diversity. Results In total, 18 studies were included, 13 of which were conducted in high-income countries. Most sources utilized longitudinal or cross-sectional data to quantify associations between CSA, sexual assault, and intimate partner/dating violence and elevated BMI/overweight/obesity/adiposity. Findings suggest that CSA perpetrated by parents/caregivers is associated with elevated BMI/overweight/obesity/adiposity via cortisol reactivity and depression; this relationship may be compounded by additional intimate partner/dating violence in adolescence. The effects of sexual violence on BMI are likely to emerge during a sensitive period of development between late adolescence and young adulthood. Emerging evidence was found regarding the relationship between child marriage (and the related exposure: age at first pregnancy) and undernutrition. The association between sexual abuse and reduced height and leg length was inconclusive. Conclusion Given that only 18 studies were included, the relationship between girls’ direct exposure to GBV and malnutrition has received little empirical attention, especially with respect to studies conducted in LMIC and fragile settings. Most studies focused on CSA and overweight/obesity, where significant associations were found. Future research should test the moderation and mediation effects of intermediary variables (depression, PTSD, cortisol reactivity, impulsivity, emotional eating) and consider sensitive periods of development. Research should also explore the nutritional consequences of child marriage.


Introduction
Childhood (defined as the time between infancy to the onset of puberty) and adolescence (between childhood and culturally/socially defined adulthood) are sensitive periods of growth and development that lay the foundation for later health status and health behaviors [1][2][3]. Adverse childhood experiences (ACEs) are traumatic events that occur during childhood and adolescence and undermine a child's physical, social, and emotional development, learning, and the sense of safety and stability [4]. ACEs can have a profound effect on later development. Examples of ACEs include witnessing or experiencing abuse or violence (such as childhood sexual abuse [CSA]), the incarceration of a parent/guardian, and having parents/guardians with substance use or mental health problems [5]. Exposure to ACEs can contribute to harmful levels of stress hormones that can negatively affect brain development and immune responses [6][7][8]. In particular, ACEs have been studied as primary exposures contributing to adult morbidity and mortality [4]. A rich body of longitudinal research has investigated relationship between ACEs and adult health. ACEs are directly associated with a greater likelihood of chronic diseases (type 2 diabetes and cardiovascular disease), mental health outcomes (depression and attempted suicide), sexually transmitted infections, and substance abuse ranging from nicotine to intravenous drugs [9][10][11][12][13][14][15][16][17].
Interpersonal violence is the intentional use of physical force or power against another person to enact physical, sexual, psychological harm, including neglect or deprivation [18]. Recent estimates indicate that interpersonal violence is the fifth leading cause of death among youth 10-24 years old, representing 3.5% of disability adjusted life years globally [19]. However, the distribution of interpersonal violence and its forms is not random. In particular, girls are disproportionately affected by gender-based violence (GBV) [20], such as dating violence/intimate partner violence (IPV) (inclusive of physical, emotional, sexual, economic and controlling behaviors); GBV is defined as the intentional or threatened use of power or physical force, against another person or group of people based on their perceived gender or gender identity [20].
In addition to dating violence/IPV, GBV also includes CSA, child marriage, female genital cutting, and marital rape [21]. GBV can be perpetrated by intimate partners, family members, peers, and authority figures, and is underscored by a gender power hierarchy, wherein "masculinity" is privileged over "femininity" and cis-gender identities are presumed to be natural and superior in comparison to trans-identities [22]. Globally, 10% of females under the age of 20 have been forced to perform sexual acts [23], while 25% of young women who have been in relationships experience IPV by their mid-twenties [24,25]. In sub-Saharan Africa, the prevalence of child marriage (defined as informal unions/marriages between a child under the age of 18 and another child or adult) is estimated to be 54.0%, ranging from 16.5% to 81.7% [26].
GBV perpetrated against females during childhood and adolescence is a specific ACE subtype (although not the only form of ACE) that can affect growth, development, and health [27]. Studies of ACEs have improved the knowledge base concerning the health impacts of GBV exposure during childhood. However, ACE studies don't disentangle GBV from other ACEs and sometimes lack sex disaggregation. Further, the majority of research exploring the health sequala of GBV focuses on violence against women specifically and examines adult morbidity specifically [28][29][30] rather than focusing on exposures and outcomes that can be measured during childhood and adolescence. Further, even when CSA is the primary interest variable, health outcomes are often measured in adulthood. Overall, there is less research exploring the childhood and adolescent health consequences of GBV perpetrated against females during childhood and adolescence.
Nutrition, a critical contributor to health and wellbeing, is defined as the process of taking in food for growth, metabolism, and repair [31]. Moreover, childhood nutritional status can impact health outcomes across the life course, with micro nutrient insufficiencies such as iron or calcium contributing to cognitive impairments and osteopenia later in life [32]. Research examining the link between GBV exposure and nutrition has predominantly focused on forms of GBV perpetrated against adult women during and immediately after pregnancy [33][34][35]. For example, IPV victimization during pregnancy and lactation negatively affects breastfeeding practices and has been linked to premature birth and labor and low birth weight, known risk factors for later childhood low height and weight for age [36]. The evidence base exploring the impact of GBV on childhood nutrition outcomes has focused on GBV perpetrated against mothers and nutrition outcomes among their children [36][37][38] (Authors, under review). Less understood are the childhood and adolescent nutritional consequences of GBV among girls who have themselves experienced GBV during childhood and adolescence.
Emerging research indicates that some nutrition-related disorders of adulthood may begin to manifest during childhood and adolescence and that exposure to GBV may contribute to the development of these disorders. Research has postulated that exposure to GBV can result in trauma and stress-related physiological processes that can affect metabolism and appetite, the development of eating disorders, coping mechanisms that influence nutrition and eating behaviors, and weight gain [39][40][41][42]. Specifically, evidence indicates that disordered eating patterns and overweight/obesity among survivors of CSA and IPV/dating violence emerge in adolescence and have enduring effects in adulthood [43,44]. Also, forms of GBV affecting girls, such as child marriage, the preferential feeding of men and boys, and controlling behaviors, may directly and indirectly impact determinants of nutrition-namely, access to nutrient-rich foods and nutrition-related services-potentially contributing to malnutrition in adolescence [45][46][47][48]. That we are aware, there is no existing evidence synthesis focused on summarizing the current body of knowledge surrounding the childhood and adolescence nutritional consequences of GBV.

Purpose
The purpose of the present research is to review and synthesize peer-reviewed, quantitative evidence describing the associations between GBV against girls and indicators of girls' nutrition outcomes during childhood and adolescence. We focus on GBV perpetrated against girls given the burden of GBV among girls and to delineate sex-specific mechanisms reported among girls. We conducted a rapid evidence assessment (REA) to describe the existing evidence-base, delineate potential causal mechanisms and pathways in the available data, and identify key methodological considerations for future empirical and theoretical research endeavors.

Methods
The present review is part of a larger REA commissioned by the United Nations Children's Fund (UNICEF). The larger REA had two research objectives: (1) Review and synthesize quantitative evidence describing the associations between GBV against girls and indicators of girls' nutrition outcomes (Direct GBV exposure) and (2) Review and synthesize the quantitative evidence describing the associations between IPV against a maternal caregiver and children's nutrition outcomes, with a particular focus on humanitarian contexts (Indirect GBV exposure). The present paper is focused specifically on the first objective of the larger REA, pertaining to the direct pathway. A separate publication details the indirect pathway (Authors, under review). There is no published review protocol. However, the protocol for the larger REA is presented in Appendix B of S2 Appendix.
We adapted the Preferred Reporting Items for Systematic Reviews and Meta Analysis standards (PRISMA) [49] for the purposes of conducting a REA. REAs adapt systematic review methodology to synthesize a body of literature, ensuring rapid completion of the review and applicability to policy and programmatic needs in a short timeframe [50]. The following changes to systematic review methodology were made: (i) title/ abstract screening was conducted by one of three reviewers and (ii) data extraction and quality assessment were conducted by a one or two team members per article, depending on whether the article warranted discussion. Furthermore, while inclusion and exclusion criteria were determined a-priori, the team iteratively refined the criteria based on the volume of sources and the overall research goal. We conducted the REA in 7 stages, which we describe below: (1) Preliminary scoping of the literature to clarify the research question and search strategy, (2) Search strategy execution, (3) Title and abstract screening, (4) Full text review, (5) Quality Assessment, (6) Data extraction, and (7) Synthesis.
As a preliminary step, we conducted a preliminary scoping of existing reviews and literature on the associations between girls' direct exposure to GBV during childhood and nutrition outcomes. We searched Google Scholar, Cochrane Reviews and PubMed for reviews concerning direct childhood exposures to GBV and subsequent nutrition-related outcomes. Selected reviews and literature were examined to elucidate specific direct pathways, select forms of GBV to include in the review, and to help operationalize database search terms.
Our preliminary scoping review indicated a general lack of robust research synthesis detailing the effect of girls' exposure to GBV on adverse nutrition outcomes during childhood and adolescence. In our preliminary scoping review, we identified the following forms of GBV experienced during childhood that are potentially related to later nutrition deficits among females: preferential feeding of boys, gendered child abuse (i.e., CSA), child marriage, and IPV/dating violence.

Eligibility criteria
Eligibility criteria were defined a-priori and then were iteratively refined to better reflect the existing body of literature and address the research question. Inclusion and exclusion criteria are displayed in Table 1. Two adjustments to the a-priori eligibility criteria were made. First, we originally wanted to focus on empirical evidence conducted in humanitarian settings.
However, due to the limited number studies detailing girls' direct exposure to GBV and nutrition related outcomes in humanitarian settings, we expanded the eligibility criteria to include studies conducted in any setting or country.
Second, we originally conceptualized the population of interest to be females up to the age of 18. However, we noted that sensitive periods of overweight development following sexual abuse or IPV occur between adolescence and young adulthood. In our title and abstract screening of the direct pathway studies, we found several longitudinal studies also measured nutrition outcomes into adulthood. In an effort not to erroneously exclude samples of children followed into adulthood, and to be consistent with the WHO definition of adolescence which extends through age 19 years, we included nutrition outcomes also measured among girls who were up to 20 years old. Although many sources recruited samples that contained both males and females, all sources included in this REA provided sex-stratified measures of association. We used these to elucidate the association between exposure to gender-based violence and nutrition indicators in females during later childhood and adolescence.

Search protocol and study selection
We conducted a structured database search in Medline, Embase, and Global Health using the Ovid Medline platform in July 2021 and in November 2022 (to capture newly published Did not measure or include the relevant direct pathway nutrition outcomes, as identified in the inclusion criteria. Studies that included mental health outcomes related to nutrition (i.e., body dysmorphia, eating disorders) but did not also measure the nutrition indicators of interest were excluded. Included nutrition-related outcomes as covariates without presenting a measure of association.

Population of interest
Girls (under 20 years) with respect to the GBV exposure(s) and the malnutrition outcome(s). Studies that included malnutrition outcomes that were measured between 18-20 years were also included a Mixed gender samples were included only if results were stratified by gender and female measures of association were presented.
Sample was exclusive to males. Sample included both males and females but did not disaggregate relevant results by gender/sex. Sample was exclusive to nutrition-related outcomes measured in adulthood.

Setting
All settings: high-middle-and-low-income countries as well as humanitarian settings and countries. a Did not restrict by setting a Denotes exclusion criteria that were determined iteratively at the full text review stage https://doi.org/10.1371/journal.pone.0281961.t001

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research). Boolean operators were used to best account for keyword and MeSH term variations. No filters, limits, or restrictions were applied to the search. Sources were exported to Covidence, a web-based software platform designed to streamline screening and full text review for systematic reviews. The S1 Appendix presents the full search strategy for each database. Screening occurred in two stages: (i) title and abstract; and (ii) full text review. Titles/ abstracts were each screened by one reviewer. Prior to conducting single screening, the team practiced screening on a sub-sample of titles/abstracts (n = 400) to ascertain and resolve any differences in interpretation regarding how to apply the inclusion and exclusion criteria. During the title/abstract screening phase, when reviewers were uncertain on how to apply the inclusion/exclusion criteria in relation to a particular source, the team discussed and reached consensus. During the full text screening, sources were assessed vis-à-vis the inclusion/exclusion criteria by two independent reviewers. Discordance between the reviewers was adjudicated by a third, independent reviewer and when necessary, further discussed with the wider team to reach consensus.

Quality assessment and data extraction
Given the diverse quantitative study designs included, no single quality assessment tool was deemed appropriate. Accordingly, the team combined relevant quality assessment questions from the following quality assessment tools: National Institutes of Health (NIH) [51], Mixed Methods Assessment Tool (MMAT) [52], Appraisal Tool for Cross Sectional Studies (AXIS) [53], Newcastle-Ottawa Scale (NOS) [54], and the National Institutes of Health assessment tool for observational cohort and cross sectional studies [55]. The items included in the quality assessment are presented in Table 2. (1) Comparability between respondents and non-respondents' characteristics is established, and the response rate is satisfactory (2) The response rate is unsatisfactory, or the comparability between respondents and non-respondents is unsatisfactory (3) No description of the response rate or the characteristics of the responders and the non-responders.
n/a a Was the violence exposure measured rigorously?
n/a a Was the nutrition outcome measured rigorously?

NIH
Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)?

NOS
(1) The statistical test used to analyze the data is clearly described and appropriate, and the measurement of the association is presented, including confidence intervals and the probability level (p value).
(2) The statistical test is not appropriate, not described, or incomplete.
a Designates quality assessment questions that were created in response to the research goals, rather than adapted The team designed a data extraction template in accordance with the research goals. Specifically, data were extracted according to general study characteristics, elements of the study design and sampling, violence exposure measurement, nutrition outcome measurement, and summary of results. The data extraction template was pilot tested for further refinement. Team members extracted information independently and extraction was reviewed by a senior member of the research team.

Synthesis
Once data extraction and the quality assessment were completed, the team reviewed the evidence base for patterns. Overarching patterns and findings with respect to study design and sampling, GBV and nutrition indicator measurement methods, overall direction of findings, and mechanisms/pathways connecting exposure to outcome were described and summarized into tables. In particular, we grouped studies by mechanism/pathway studied and synthesized overall results according to mechanism/pathway. Quality assessment measures were summarized using aggregate descriptive statistics (count frequencies and percentages). See S2 Appendix for disaggregated quality assessment results.

Results
The PRISMA flow diagram is presented in Fig 1. After executing the database search strategies, 6493 sources were imported to Covidence and 1516 duplicates were removed, yielding 4977 citations for screening. During title and abstract screening, 4461 sources were excluded, and 468 full texts were assessed for eligibility. During full text review, 450 sources were excluded for various reasons outlined in Fig 1. In total, only 18 represent the direct pathway and are included in this paper. Table 3 displays general characteristics for the 18 studies examining pathways between girls' GBV exposure and indicators of nutrition outcomes during childhood and adolescence. Although more than half of studies were conducted in high-income settings, several studies reported outcomes in low-and-middle income countries. The specific countries included were Ethiopia (n = 1), Nepal (n = 1), Brazil (n = 2), Mexico (n = 1), as well as United States (n = 8), England (n = 2), and the Netherlands (n = 2), with one study combining data from the United Kingdom and Brazil (n = 1).

Study characteristics
Most sources sought to quantify associations between specific forms of sexual violence affecting children, including girls, and indicators of subsequent nutrition status in childhood and adolescence. Some studies conducted analyses that permit more nuanced understandings of causal mechanisms including use of community-based comparator groups [56][57][58][59]; moderation by cortisol reactivity [57]; moderation by HPA axis attenuation [41]; interaction of caregiver abuse and IPV/dating violence [60]; interaction of child marriage and age at first pregnancy [61]; and stratification by age [62] and developmental period [56].

Quality assessment
In Table 4 we present the quality assessment results. Key gaps in quality were due to high attrition/non-response, poor measurement of GBV, and limited external validity/generalizability due to the sampling of selected groups. All studies (100%) had clearly stated research questions and objectives. Studies varied in terms of external validity and representativeness, with 55.6% of studies being truly representative of the target population and 38.9% representing a selected group, for example, cases of child abuse reported to Child Protective Services. Less than half of studies (38.9%) achieved satisfactory response rates (meaning less than 10% attrition/nonresponse) and/or comparability between respondents and non-respondents. The measurement of girls' exposure to gender-based violence was deemed rigorous in half of the included studies (50.0%) and the measurement of childhood nutrition-related outcomes was appropriately rigorous in 83.3% of the included studies. Rigorous measurement of GBV and nutrition was assessed using a variety of indicators including, whether the variables were clearly defined, accurately measured and applied consistently, measurements were justified and appropriate for answering the research question, measurements reflected what they are supposed to measure, measures were collected using validated and reliability tested tools/instruments/questions, variables were measured using 'gold standard' tools, and questionnaires were pre-tested prior to data   Table 5 presents participant recruitment and sample details. Gender-stratified samples ranged from under 100 females [56] to over 26,000 [63]. The range of sample sizes is a reflection of the study designs utilized; studies with smaller sample sizes focused on newly reported cases of CSA obtained from Child Protective Services [41,[56][57][58][59], or other similar organizations such as a clinic for victims of child abuse [64], and larger sample sizes pertained to secondary data analyses of nationally representative and/or longitudinal datasets of child and adolescent health [60,62,63,[65][66][67][68][69][70][71]. Sampling of CSA cases from Child Protective Services is a valid method for capturing this form of GBV given that cases of genital contact and/or perpetration by family members are investigated and substantiated according to national laws. In such studies, the survivor children and a non-abusing caregiver(s) are referred to the study within a specific time frame (i.e., 6 months) of the initial abuse disclosure. However, sampling of CSA cases from Child Protective Services may not represent the entire population of CSA cases given that only a proportion of children who experience this form of abuse formally enter the child protection system. Socio-economic status and racialization experiences (as well as other social determinants of health) may differ between CSA cases that formally enter protection systems and cases that are unreported, thereby potentially introducing sampling bias and limiting generalizability. The majority of studies included samples of adolescent participants or samples in which participants were adolescents/young adults at final data collection; although Martin-Martin et al. [64] specifically focused on children ages 0-11 years. Participant recruitment strategies varied across the sources and included both probability (n = 11) and non-probability samples (n = 7). Two predominant study designs were utilized: (i) longitudinal-including panel, prospective cohort, and cross cohort comparison designs-(n = 12) and (ii) cross sectional (n = 6). Thirteen studies conducted secondary analysis on existing datasets.

Nutrition indicators
Nutrition indicators relied on anthropometric measures that were either observed or selfreported (Table 7). Body mass index (BMI) was the most used nutrition indicator included in the studies of older children and adolescents. In addition, other nutrition indicators that were assessed included height for age, weight for height, height for younger children, leg length, waist circumference, fat mass index, android fat percentage, mid-upper arm circumference (MUAC), and anemia among the older children and adolescents. Height and weight were assessed using either anthropometric measurements [41, 56-61, 64, 66, 67, 69-71] or selfreported height and weight (which may be affected by recall error or bias based on context dependent body ideals) [63,69,72]. Either weight for height or BMI were calculated as appropriate according to participants' ages and operationalized for analysis using different methods [73,74]. (2) The response rate is unsatisfactory or the comparability between respondents and non-respondents is unsatisfactory 10 55.6% (3) No description of the response rate or the characteristics of the responders and the non-responders. 1

Results
Is the nutrition outcome measured rigorously? Yes 15 83.3% Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)?

Statistical test
The statistical test used to analyze the data is clearly described and appropriate and the measurement of the association is presented including confidence intervals and the probability level (p value) 14

77.8%
The statistical test is not appropriate not described or incomplete.

22.2%
https://doi.org/10.1371/journal.pone.0281961.t004 The participants who were exposed to maltreatment were referred by the LA County Department of Children and Family Services. Participants were contacted via post card and phone call. The comparison group was created by consulting school lists of children 9-12 from the selected zip codes of the maltreatment sample. Parents/caregivers of the children were contacted via postcard and phone call.

No
Selected group (i.e. clinic-based sampling in hospital) The participants who were exposed to maltreatment were referred by the LA Count Department of Children and Family Services. Participants were contacted via post card and phone call. The comparison group was created by consulting a list obtained from a marketing firm to recruit children 9-12 from the selected zip codes of the maltreatment sample. Parents/ caregivers of the children were contacted via postcard and phone call. The participants who were exposed to maltreatment were referred by the LA Count Department of Children and Family Services. Participants were contacted via post card and phone call. The comparison group was created by consulting a list obtained from a marketing firm to recruit children 9-12 from the selected zip codes of the maltreatment sample. Parents/ caregivers of the children were contacted via postcard and phone call. Height and leg length were assessed longitudinally throughout childhood and adolescence in Denholm et al., [62]. Multiple measures of adiposity were measured by Soares, et al., [67] using anthropometric measurements and dual-energy x-ray absorptiometry scans in adolescents. 'Anemia' during adolescence was measured in only one study using a point of care diagnostic lab test for hemoglobin and operationalized using WHO defined thresholds and presuming iron deficiency without documenting iron/ferritin levels [68].

Synthesis of findings
The 18 included studies addressed three pathways describing associations and potential mechanisms between exposure to GBV during childhood/adolescence and nutrition indicators. Study results are displayed in Table 8. Overall, findings indicate that sexual abuse (for example, CSA, IPV, dating violence) experienced during childhood and adolescence was positively and significantly associated with elevated BMI, overweight, obesity, and adiposity, particularly when studied longitudinally. We found more limited evidence with respect to the relationship between child marriage and undernutrition (anemia, BMI, MUAC, and chronic energy deficiency). We outline the three pathways below, with a focus on summarizing results and describing important methodological implications. Pathway 1: Exposure to sexual abuse during childhood and adolescence and later elevated BMI (i.e., overweight, obesity) or increased adiposity Pathway 1a: Exposure to sexual abuse by trusted adults during childhood and adolescence and later elevated BMI (i.e., overweight, obesity) or increased adiposity. Overall, the evidence suggests that CSA perpetrated by parental/caregiver figures is associated with later increases in BMI, including overweight/obesity in late adolescence and early adulthood. Ten studies specifically explored this pathway, five of which were conducted in children referred for maltreatment in the U.S. [56][57][58][59], with three reporting on the same longitudinal study cohort of maltreated children in Los Angeles [L.A.] [57][58][59]. In this longitudinal cohort study, there was no increase in BMI associated with exposure to sexual abuse during childhood and early adolescence [58], but rather increased BMI trajectory was apparent only during middle to late adolescence when compared with girls exposed to no violence or physical violence only [59]. Another U.S. based study of children referred for maltreatment similarly found that by young adulthood, females who had experienced sexual abuse in childhood were more likely to be obese, compared with those not abused [56]. Further, Peckins et al.'s (2019) [57] analysis on the L.A. cohort suggests that response to stress measured through cortisol reactivity may act as   [71]. Among females, CSA was positively related to BMI at wave 5 only and CSA was positively related to MDD and GAD, which in turn were positively related to BMI at wave 4. Among males, there was no relationship between CSA and BMI or the mental health mediators and BMI. Together these studies suggest that the effects of sexual abuse on elevated BMI emerge during late adolescence and young adulthood for females. Further, low cortisol reactivity could be a risk profile for greater BMI in late adolescence among girls exposed to child sexual abuse, compared to those unexposed and those exposed to physical abuse. When longitudinal BMI data was analyzed cross sectionally, insignificant associations between CSA and BMI were noted [67,69,70] and when cross sectional data were used relationships indicating CSA has a protective effect on elevated BMI [58]. Pathway 1b: Exposure to intimate partner/dating violence and sexual violence during adolescence and later elevated BMI. There is some evidence highlighting the risk of elevated BMI following exposure to sexual violence (perpetrated by any perpetrator, not specific to trusted adults such as parents/caregivers) and intimate partner/dating violence. In total, five studies examined the pathway between exposure to intimate partner/dating violence and sexual assault/rape perpetrated by intimate and non-intimate partners and elevated BMI among girls. The strongest evidence emerged from Clark et al., (2014) [60] who explored the pathway between exposure to dating violence/IPV (physical and sexual combined) and elevated BMI, finding that exposure to intimate partner/dating violence was positively associated with increasing BMI. Exposure to CSA and adolescent exposure to intimate partner/dating violence was further positively associated with elevated BMI. Marques et al. (2021) examined the relationship between exposure to rape and overweight/obesity among female adolescents over 13 years in Brazil, concluding that rape was positively and significantly associated with overweight and obesity among girls [66]. Veldwijk et al., (2012) [63] analyzed the relationship between sexual assault perpetrated by adults or peers and the presence of underweight, overweight, and  Weight for height (in children less than 60 months of age) using WHO cut points and Z score thresholds (>2SD); BMI using Z score thresholds in children 5-11 years; Underweight defined using weight for age in children less than 60 months using WHO criteria and z scores; Stunting using WHO criteria (height for age) and Z scores (>2SD) Infant, toddlers, Pre-school (3 months-5 years); School age children (5)(6)(7)(8)(9)(10)(11) years) 0-23 months; 0-59 months; 5 to 9 years; 10-19 years (Continued )

Pathway 2: Exposure to child marriage and undernutrition
Only two studies examined child marriage and measures of undernutrition (anemia, MUAC, BMI, chronic energy malnutrition [BMI < 18.5kg/m 2 ]) [61,68]. We found one study reporting an association between girl child marriage and anemia. This study analyzed the Ethiopian  1) 21% of 29 girls < 5 had low 'emaciated' weight for height in those who suffered physical abuse in those < 5; while none among those 26 who had suffered sexual abuse. chi-square 6.08, p<0.01 2) 48% of 29 girls< 5 had low height for age in those who suffered physical abuse in those < 5; while 3 (12%) among those 26 who had suffered sexual abuse. chi square 8.66 p<0.005

No No
No Girls <5 years who were victims of physical abuse were more likely to be underweight and stunted than those who were victims of sexual abuse (no adjustment), chi square only. Among children ages 5-11, girl victims of physical abuse were more likely to be underweight (by BMI), stunted, than girls victims of sexual abuse, while girls victims of sexual abuse were more likely to be overweight or obese (than those who had suffered physical abuse).
(Continued ) (2) Sexual abuse vs non-abused comparator: 0.29(0.14) � Girls exposed to sexual abuse has a slower increase in BMI percentile (compared to those unexposed), until 16-17 years of age, when BMI percentile was higher than girls in the comparison group Race/ethnicity pubertal stage, psychological functioning (depression, anxiety)

No
(1) Sex/Gender Girls exposed to a history of maltreatment had different BMI grown trajectories than comparator/unexposed girls. At 15-16 years old, comparator group BMI decreased and girls with sexual abuse had higher BMI (analyzed on a quadratic scale).
(Continued )  Age, sex, ethnicity, maternal education, paternal education, and parental social class

No
(1) Sex/Gender Higher BMI at age 18 was associated with sexual abuse in the unstratified sample. However, this was only true among the male portion of the stratified sample, and was not evident in the female stratified sample. Dating violence was a significant predictor of increased BMI over time among females and exposure to childhood abuse magnified the BMI increase among those exposed to dating violence. No associations in males were noted.
(Continued ) national Demographic and Health Survey data, finding that a history of child marriage among girls was significantly and positively associated with anemia (low hemoglobin) in adolescence [68]. The study did not examine history of childbirth. A second study using data from Nepal, investigated the relationship between age at marriage and age at first pregnancy and the outcomes of BMI, MUAC, and chronic energy deficiency [61]. The interaction between age at marriage and age at first pregnancy was significant in the BMI outcome model and marginally significant in the MUAC outcome model. For women who first became pregnant at age 15 or less, marriage at earlier ages resulted in significantly lower BMI at endpoint, compared to those who were married later. For women whose first pregnancy occurred at age 19 or higher, earlier marriage was associated with higher BMI. Pregnancy at age 15 or lower was positively associated with chronic energy deficiency, compared to pregnancy at 19 years or older.

Pathway 3: Exposure to childhood abuse (including sexual) and reduced height and leg length
One study investigated the relationship between child abuse (including sexual abuse) perpetrated by parents/caregivers and reduced height and leg length among girls [62]. The study found that leg length at age 16 was not associated with number of abuse types experienced, witnessing violence, or with overall maltreatment scores among females. Further, sexual abuse was not significantly associated with adult height.

Discussion
We conducted a REA to synthesize quantitative evidence describing associations between girls' exposure to GBV and indicators of nutrition status during childhood and adolescence. Overall, the evidence base is limited: only 18 studies met our inclusion criteria and most studies examined either CSA or IPV/dating violence with later overweight/obesity/measures of adiposity. Our review indicates the lack of studies investigating the potential impacts of exposure to GBV on indicators of childhood and adolescence nutrition status among females; in particular, nutrition outcomes beyond those calculable with measures total body height and weight, indicators of key nutrient levels (including iron deficiency), or more sensitive indicators of growth during specific developmental periods. Beyond CSA, dating violence/IPV, and child marriage, no other forms of GBV were studied in relation to girls' nutrition indicators.
Another form of GBV that warrants empirical attention is the preferential feeding of boys which could be relevant in humanitarian/fragile settings where there may be high levels of food insecurity [46,[76][77][78]. Expansion of this evidence base in LMIC is also needed, with

No
(1) Sex/Gender: (2) Age at follow up (7,11,16,Adult) No significant association between abuse and witnessing abuse among females and height and leg height by 16 years. However, overall, the study found that childhood neglect and household dysfunction assessed at 7 years was associated with shorter stature among both males and females https://doi.org/10.1371/journal.pone.0281961.t008

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appropriate study designs and analytical procedures that account for high baseline levels of malnutrition and multi-level risk factors for malnutrition. Our synthesis elucidated three potential pathways linking exposure to GBV and indicators of subsequent childhood and adolescence nutrition status among females: 1. Exposure to sexual abuse by a) parents/caregivers during childhood (CSA) and later elevated BMI (i.e., overweight, obesity) or increased adiposity, b) IPV/sexual violence during adolescence and later elevated BMI (i.e., overweight, obesity) or increased adiposity. The evidence base most clearly and consistently supported this pathway, given most studies analyzed sexual violence and BMI/obesity/overweight/increased adiposity outcomes.
2. Exposure to child marriage and undernutrition (amenia, chronic energy deficiency, and MUAC). There is emerging evidence supporting this pathway. However, additional research is needed to replicate the findings of the two studies investigating child marriage and undernutrition. Importantly, age at first pregnancy appears to be a consequence of girl child marriage or an impetus for girl child marriage that has negative nutritional consequences for adolescent females.
3. Exposure to childhood abuse (including sexual) and reduced height and leg length. The evidence base is inconclusive regarding this pathway, given only one study with insignificant results was found.
Among the included studies, the strongest and most consistent evidence supports the relationship between elevated BMI in late adolescence and early adulthood and exposure to sexual abuse during childhood (CSA) or adolescence (intimate partner violence/sexual assault/rape). Childhood and adolescent exposure to sexual violence, perpetrated by parents/caregivers and intimate partners, is an important predictor of nutrition status indicators in childhood and adolescence among females. Understanding the biological mechanisms that underlie this association may help guide further research regarding the consideration of intermediary variables, timing of causal effects, prevention efforts, and actionable periods of intervention.
CSA and exposure to IPV in adolescence are examples of ACEs, however health impacts are largely measured in adulthood and nutrition outcomes are less considered compared to chronic disease, mental health, and substance use. This is an important research gap given that findings from this REA indicate nutrition outcomes such as adolescent obesity are associated CSA, IPV, and sexual assault/rape exposure during childhood and adolescence. To further understand mechanisms that link GBV exposure in childhood/adolescence and the early emergence of nutrition disorders, additional research that considers childhood and adolescence nutrition outcomes is needed.
Our findings highlight that sexual violence, either perpetrated by parents/caregivers during early or middle childhood or by intimate partners or strangers later on in adolescence, is a stress-inducing form of trauma which engenders nutrition-related consequences in childhood and adolescence (as seen in this review), and into adulthood [15]. Previous studies have linked ACEs, including CSA and sexual violence, to stress response dysregulation [41,[79][80][81]. Like other ACEs, the biological mechanism linking sexual violence to elevated BMI likely involves the hypothalamic-pituitary-adrenocortical (HPA) axis (although, other pathways may also be involved). The HPA axis modulates the stress response by regulating the secretion of cortisol in response to environmental conditions perceived as being stressful and beyond an individual's capacity to cope [7,82,83]. Exposure to sexual violence in early childhood and adolescence can serve to activate the HPA-axis in a manner that can negatively affect health outcomes related to nutrition, mental health, and immunity [79]. Long term or chronic activation of the HPA-axis from exposure to GBV and other adversities results in an attenuated diurnal decrease in cortisol or dampened/attenuated cortisol reactivity [57,82], thus chronic exposures to GBV may be especially harmful.
Higher values of initial cortisol levels followed by a lowered rate of cortisol increase is characteristic of HPA axis dysregulation. Dampened or attenuated cortisol reactivity occurs when the HPA axis adapts to prolonged stress-induced cortisol secretion. The downregulation of basal cortisol secretion is a protective mechanism to mitigate the negative consequences of elevated cortisol. For adolescent girls, cortisol dampening/attenuation can negatively interact with normal pubertal physiological maturation, increasing the risk of developing overweight/obesity and adiposity. Biochemical pathways (metabolic disturbances, altered insulin signaling, inflammation induced damage to leptin and insulin receptors), behavioral pathways (increased impulsivity and related overeating), and/or the interaction between biochemical and behavioral pathways may explain how cortisol attenuation/dampening is related to overweight/obesity and adiposity [41,[84][85][86]. We did not locate any studies that considered eating patterns as intermediary variables between GBV and elevated BMI/overweight/obesity/adiposity, limiting a nuanced understanding of the behavioral pathway and its connection to the biochemical pathway.
Research focusing on childhood GBV has demonstrated that among girls who have experienced CSA, while initial cortisol levels following sexual abuse exposure may be high, there is a developmental transition to lower levels of cortisol in early adulthood via cortisol attenuation [87]. More recently, research supports associations between cortisol attenuation and CSA exposure in later childhood and early to mid-adolescence (ages 6-16) among females, wherein serum basal cortisol levels further decreased longitudinally into adulthood [41]. Cortisol attenuation over time (from childhood to adulthood) was also associated with an accelerated rate of BMI accumulation across development (late childhood, adolescence, and early adulthood) and completely mediated the effect of CSA on accelerated BMI accumulation over development [41]. In the articles we reviewed, exposure to sexual abuse in school aged girls was associated with elevated BMI in late childhood, peri-puberty (ages 6-11), and late adolescence into early adulthood. Importantly, we noted that in  [66], such relationships were only noted among girls, thereby suggesting the importance of conducting a sex-stratified analysis. Other studies have also examined the nutritional impact of adverse childhood life events, including one systematic review focused on the relationship between ACEs more generally and childhood obesity among both boys and girls, which highlighted that sexual abuse appears to have a greater effect on childhood obesity than other ACEs and particularly among girls [43].
The currently synthesized evidence base and the wider literature presents mixed results for sex and/or gender differences in HPA axis attenuation following exposure to chronic stressors and nutrition outcomes involving elevated BMI/obesity/overweight/adiposity. Additionally, there is paucity of tested biological and social mechanisms that account for any sex/gender differences noted. Compared to males, females may be more susceptible to stress-related disorders that impact eating behaviors [88]. Adolescent females also have estrogen-related elevated central adiposity due to hormonally regulated differences in fat distribution, with females developing higher subcutaneous and gluteofemoral fat [89]. In addition, GBV exposure distribution may differ by gender: girls are at greater risk for poly-victimization (cumulative exposure to CSA, sexual IPV/dating violence, and non-partner rape across childhood and adolescence) compared to boys, thereby translating to a dysfunctional stress responses characterized by cortisol attenuation and internalized mental health sequela [90,91].
Future research investigating the relationship between exposure to CSA and IPV or dating violence among females could consider the inclusion of theoretically relevant intermediary variables. Other potential mechanisms beyond dampened/attenuated cortisol reactivity may also include mental health mediators, given that CSA can lead to mental health disorders and negative affect. For example, 'emotional overeating' at age 10 has been associated with exposure to adverse events in younger children [92]. Gaining weight by overeating may also be perceived as a means of deterring unwanted sexual attention/advances among girls previously exposed to CSA [41,93]. It is important to also consider the role of eating disorders, PTSD and depression as mediator or effect modification variables. Only Elsenburg et al., (2022) considered the mediating role of major depressive disorder and generalized anxiety disorder on the relationship between CSA and BMI among young adults, reporting that CSA is positively associated with major depressive disorder which is in turn positively related to BMI for females but not males [71]. Other research has shown that among survivors of sexual violence, a transition from acute cortisol hyper-reactivity to prolonged hypo-reactivity is characteristic of posttraumatic stress disorder among females (PTSD) [79]. Depression is also of relevance: in a meta-analysis, Danese and Tan (2014) established that when estimates were adjusted for current depression, the relationship between childhood maltreatment (including sexual abuse) and obesity became insignificant [9]. Thus, studies can consider depression as a potential intermediary variable given it is likely a consequence of GBV and can affect nutrition outcomes. Lastly, research could also consider protective factors among children exposed to ACEs, including GBV, and how protective factors such as, quality education, presence of role models, and school/extracurricular engagement, and mental health supports [94,95], can moderate the development of adverse nutrition outcomes.
We also noted that the effect of childhood exposures to sexual violence on elevated BMI, overweight/obesity/adiposity manifests during sensitive periods of adolescent development into early adulthood. Scholarship has focused mainly on elucidating at what developmental periods childhood maltreatment generally impacts elevated BMI and obesity, with late adolescence/early adulthood emerging as a sensitive period [9,96]. For example, Sokol et al., (2018) [97] tested childhood exposures to physical, sexual, and emotional abuse and found that these yielded different BMI growth trajectories between the ages of 13 to 28 years for males and females. Importantly neither of these studies included examination of pre-pubertal growth trajectories, thus potential earlier impacts are unknown. In particular, girls' exposure to sexual abuse between 13 and 17 years was positively associated with BMI in late adolescence to early adulthood, from 19 to 24.5 years of age [96]. A meta-analysis of over 40 studies reported a higher risk of obesity in adulthood, following exposure to child maltreatment, not childhood/ adolescence [9]. However, the meta-analysis included few studies that examined exposure to sexual abuse with nutritional indicators measured during childhood and adolescence, as the majority of studies examined nutritional status measured in adulthood [9]. Thus, further research examining exposure to sexual violence with nutrition indicators measured during earlier developmental periods (including prior to and through adolescence into early adulthood) is needed.
Overall, we recommend further clarifying the linkage between GBV and nutrition during childhood and adolescence in females. There is a research-related gap in theorizing and empirically testing mechanisms that aim to explain how and why GBV against girls negatively impacts their nutritional status during later childhood and adolescence. The present REA found evidence to support associations between exposure to sexual violence during childhood and adolescence and elevated BMI/overweight and obesity later in childhood and adolescence. However, nuanced understandings of the causal mechanism underlying this pathway are limited. Given that adolescence represents a period of potential growth catch up and can coincide with pregnancy and child rearing [98], it is important that future studies consider measuring nutritional status among adolescent girls.
From a methodological standpoint, future research should specifically examine exposure to sexual violence when examining nutrition indicators in younger children. Sexual violence exposure can be disaggregated from other ACEs and measured by timing of exposure [infancy, early childhood, middle childhood, or adolescence; or by pubertal stage] and perpetrator type [family member/relative/caregiver, intimate partner, peer, stranger]). Important mediator variables include measures of behavioral changes (internalizing [emotional eating, low self esteem] and externalizing [aggression]), mental health symptoms and disorders (depression, PTSD, eating disorders), impulsivity, and dampened/attenuated cortisol reactivity. Further research can elucidate sensitive periods for anthropometric measures vis-à-vis exposure to sexual violence. Prospective longitudinal collection of informative biomarkers beginning early in childhood among potential at-risk populations will be key for improving our understanding of the relationship between exposure to sexual violence, a dysregulated stress response (including measures of behavior and mental health), and later elevated BMI. Research aiming to investigate the effect of exposure to sexual violence during childhood and adolescence on elevated BMI should consider longitudinal study designs that measure BMI into early adulthood to include sensitive periods of development. Sex-stratification of data could also elucidate sex and gender specific mechanisms, particularly given the sex-based differences in timing of developmental stages. Greater attention should be given to the temporal sequence of variables. For example, measuring mental health symptoms/disorders in parallel with nutrition outcomes can obscure the correct temporal sequence between mental health intermediaries and nutrition outcomes. Accurately capturing cortisol dampening/attenuation requires that investigators measure diurnal serum cortisol variation according to the circadian rhythm.
Our findings should be interpreted in light of some limitations. We conducted single screening of titles and abstracts (a single reviewer determined whether to include or exclude). Although in line with guidance on how to adapt systematic review methodology for an REA [99], single screening of titles and abstracts may have excluded relevant studies. Further, disparate use of outcome measures may mean that results from specific studies are not directly comparable. Lastly, we excluded articles in languages other than English and Spanish due to resources and time-constraints.

Conclusion
This REA identified a small evidence base of 18 quantitative studies investigating the association between GBV perpetrated against girls and subsequent child and adolescent nutrition outcomes. Only two studies investigated the relationship between child marriage and undernutrition, indicating the need for greater attention paid to the nutritional consequences of child marriage on girl brides and the importance of considering age at first pregnancy within the context of girl child marriage. Most included studies investigated the relationship between the outcomes of overweight/obesity/increased adiposity and the exposures of CSA, IPV, and dating violence. We recommend consideration of relevant intermediary variables and timing of effects, pertaining to the biologic mechanisms underlying the relationship between childhood GBV exposure and overweight/obesity. Future research is needed to not only better understand the mechanisms that underlie the relationship between childhood sexual violence exposure and overweight/obesity, but also consider other GBV exposures such as child marriage, the preferential feeding of boys on nutrition outcomes beyond overweight/ obesity, and additional research in LMIC, resource poor and humanitarian settings. 99. Garritty C, Gartlehner G, Nussbaumer-streit B, King VJ. Cochrane Rapid Reviews Methods Group offers evidence-informed guidance to conduct rapid reviews. 2020;(January).